Optical device for bar-cord reading, method for manfacturing thereof, and light projection/receiving package

ABSTRACT

An optical device for bar-code reading capable of improving the degree of freedom in design of component lenses so as to allow free positional adjustment of the lenses while ensuring downsizing and weight reduction of the device per se, and a method for manufacturing thereof are disclosed. An optical device for bar-code reading comprises a light emitting element; a light projection lens for focusing light from the light emitting element so as to irradiate a bar code; a light receiving lens for focusing reflected light from the bar code and having formed therein a penetrating hole which penetrates a plane of incidence of light and a plane of outgoing of light, in which the light projection lens is inserted; and a light receiving element for receiving the light focused by the light receiving lens so as to perform photo-electric conversion.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The present invention claims priority to its priority documents No. 2001-156508 and No. 2001-184725 filed in the Japanese Patent Office on May 25, 2001 and Jun. 19, 2001, respectively, the entire contents of which being incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an optical device for bar-code reading and a method for manufacturing thereof, in particular to those capable of improving the individual degrees of freedom in design and positioning accuracy of a light projection lens and a light receiving lens in an integrated constitution; and also to a light projection/receiving package for bar-code reading, in particular to that capable of improving downsizing of the package through minimizing an area for mounting a light emitting element and a receiving element.

[0004] 2. Description of the Related Art

[0005] Many of recent shops and factories practice sales management of commodities or production management of products by attaching thereto bar codes indicating digital information of the products, and by reading such information through optical scanning thereof. In a general procedure using such kind of bar code, light is irradiated to a bar code and reflected light therefrom is processed by photo-electric conversion depending on the intensity of the reflected light, to thereby decode the information based on a combined pattern of detected signals.

[0006] More specifically, as schematically shown in FIG. 19, a light projection lens 3 focuses light emitted from a light emitting element 1, and thus focused light is irradiated to a bar code 9 after being reflected off a mirror 7 of a scan mirror 5. The mirror 7 is swung so as to irradiate the entire area of the bar code 9. The swinging of the mirror 7 is based on attraction and repulsion of a magnet 11 attached to the mirror 7 to or from a drive coil 13 into which the magnet 11 is inserted, where the drive coil 13 is applied with positive and negative currents inverting at a predetermined cycle to thereby swing the mirror 7 around a fulcrum of swinging 15.

[0007] The light irradiated on a surface of the bar code 9 returns back to the mirror 7 with an intensity variation caused by a black-and-white pattern of the bar code 9 while being affected by some irregular reflection. A condensing lens 17 then focuses the light reflected there, and a light receiving element 19 electrically converts the intensity variation to thereby produce an output. The light receiving element 19 herein has provided on a front surface thereof with a band-pass filter (BPF) 21 for improving accuracy in the reading, to thereby successfully prevent unnecessary light having a frequency other than the emission frequency from being caught.

[0008] There has been provided an optical device for bar-code reading as shown in FIG. 20, which materializes such reading system. As illustrated in the drawing, the device comprises a light emitting assembly A having a light emitting element 1 and light projection lens 3 housed in a casing 25, and a light receiving assembly B having a light receiving element 19, a light receiving lens 17 and a BPF 21 housed in a casing 27, both assemblies being mounted on a substrate 29. Electrical connections within the individual casings 25, 27 are accomplished through wire bonding or the like. The mirror 7 of the scan mirror 5 is arranged so as to allow swinging around the fulcrum of swinging 15. The light emitting assembly A, the light receiving assembly B and the scan mirror 5 are housed in a housing not shown, to thereby form an optical device for bar-code reading.

[0009] The foregoing optical device for bar-code reading however requires a large mounting space and can attain only a limited range of downsizing since the light emitting assembly having the light emitting element and light projection lens housed in the casing, and the light receiving assembly having the light receiving element and the light receiving lens in the casing are separately composed.

[0010] As measures for solving such non-conformity, there is known a “bar-code reader” as disclosed in Japanese Patent Application Publication No. Hei 7-93454, in which two lens portions are integrated into one transparent lens to thereby downsize a device as a whole, and a “bar-code reading device” as disclosed in Japanese Patent Application Publication No. Hei 11-15910, in which an irradiation lens and an imaging lens are formed using a transparent resin material in an integrated manner to thereby reduce the number of optical parts and save labor for assembly.

[0011] While these devices were successful in achieving a certain degree of space saving, it has not been allowable to choose different media as being optimized for the light emitting characteristics and the light receiving characteristics, since the light projection lens portion and the light receiving lens portion are molded in an integrated manner within a single kind of transparent resin used as a medium. It has also been difficult to compose either lens as a compound lens, or to provide different coatings for the individual lenses, which has limited design of such lenses. Still another problem resides in that such kind of integrated mold lens cannot allow moving of either lens once the other lens is properly positioned and fixed, which inhibits precise positioning by finely adjusting positions of both lenses on the light emitting side and the light receiving side.

[0012] An electro-optical reading device as disclosed in Japanese Patent Application Publication No. Hei 11-326805 is such that having a semiconductor laser chip (light emitting element) and a photo detector (receiving element) mounted side by side on one surface of a printed circuit board, where all of which are covered with a mold resin member. To the mold resin member, a lens, a prism and an opening are molded in an integrated manner so as to allow the laser light from the semiconductor laser chip to be focused, to be bent in the optical path thereof and to be emitted, and that further having a concave mirror for focusing the returned light towards a photo-detector, to thereby achieve downsizing and weight reduction. The device however inevitably has a large printed circuit board due to planar arrangement of the semiconductor laser chip and photo-detector side by side on one surface of the printed circuit board, so that the downsizing cannot be attained to a satisfactory level.

[0013] The present invention was proposed considering the foregoing situation, and provides an optical device for bar-code reading capable of improving the degree of freedom in design of the component lenses so as to allow free positional adjustment of such lenses while ensuring a small size and light weight of the device per se, and a method for manufacturing thereof.

[0014] Furthermore, the present invention was also proposed considering the foregoing situation, and provides a light projection/receiving package in which keeping an area sufficient for mounting of either one of light emitting element and receiving element enables mounting of the other element, to thereby achieve downsizing and weight reduction of the package.

[0015] As has been detailed in the above, since the light projection/receiving package according to the second aspect of the present invention is composed so that a light emitting element and a light receiving element are mounted back to back on front and rear planes of a single die pad, it is no more necessary to keep both areas for mounting the light emitting element and the light receiving element on one plane (on the same plane) of the die pad. Accordingly, it will be sufficient to use a die pad affording a mounting area for either element requiring a larger mounting area, and this intrinsically allows mounting of the other element on the opposite plane. That is, only a small die pad affording a mounting area for either of the light emitting element and the light receiving element allows mounting of the both. This successfully results in downsizing and weight reduction of the light projection/receiving package.

SUMMARY OF THE INVENTION

[0016] An optical device for bar-code reading according to a first aspect of the present invention comprises a light emitting element; a light projection lens; a light receiving lens; and a receiving element. The light projection lens focuses light from the light emitting element so as to irradiate a bar code. The light receiving lens focuses reflected light from the bar code and has formed therein a penetrating hole penetrating a plane of incidence of light and a plane of outgoing of light, in which the light projection lens is inserted. The light receiving element receives the light focused by the light receiving lens so as to perform photo-electric conversion.

[0017] In the optical device for bar-code reading, a space for mounting the light receiving lens essentially include a space for mounting the light projection lens by forming a penetrating hole through the light receiving lens and by inserting the light projection lens into the penetrating hole. Accordingly, it is no more necessary to provide a mounting space for every lens, which results in downsizing and weight reduction. In addition, it allows selection of material and coating or so optimized for each lens to thereby expand possibility in design. It is also advantageous in that positions of the light projection lens and the light receiving lens can independently be adjusted so that positional errors of the individual lenses relative to the individual elements (light emitting element and receiving element) can surely be absorbed.

[0018] The optical device for bar-code reading of the first aspect of the invention may be modified so that the light projection lens thereof is a compound lens in which a plurality of single lenses are combined.

[0019] In the optical device for bar-code reading, the light projection lens is composed as a compound lens. The compound lens comprises a plurality of single lenses combined with each other. In this case, typically composing the compound lens so that light can propagate almost in parallel between two lenses will ensure a large allowance for axial dislocation in a direction normal to the optical axis, which is effective in terms of improving production yield and reliability.

[0020] The optical device for bar-code reading may also further modified so that the plurality of single lenses are fitted within a cylinder. They are arranged so that an optical axis of the lenses coincides with an axis of the cylinder, and the cylinder is inserted in the penetrating hole of the light receiving lens.

[0021] Since the optical device for bar-code reading is composed so that a plurality of single lenses are fitted within a cylinder, and the cylinder is inserted in the penetrating hole of the light receiving lens, a variety of positional adjustment of the lenses will be available, for example such that moving the whole compound lens, previously fabricated so as to arrange the single lenses within the cylinder at regular intervals, relative to the penetrating hole, or such that moving an arbitrary single lens relative to the cylinder while keeping the cylinder being fixed in the penetrating hole.

[0022] The optical device for bar-code reading may be further modified so that the cylinder is made of a metal.

[0023] As for the optical device for bar-code reading, composing the cylinder with a metal can desirably prevent the light, which comes from the light emitting element and goes into the compound lens, from propagating from an inner circumferential surface of the penetrating hole towards a medium of the receiving lens. Accordingly, it is no more probable that the light from the light emitting element comes into the receiving element to cause disturbance. In other words, the receiving element can gain a higher receiving accuracy of the reflected light.

[0024] The optical device for bar-code reading of the first aspect of the invention may also modified so that the light projection lens is a cylindrical single lens.

[0025] As for the optical device for bar-code reading, composing the light projection lens with the cylindrical single lens can facilitate the manufacturing thereof as compared with that of the forgoing compound lens. The cylindrical shape allows the light projection lens per se to be inserted into the penetrating hole, so that the light projection lens is now attachable to the light receiving lens in a manner freely movable along the optical axis without using any other members (the foregoing cylinder for example).

[0026] The optical device for bar-code reading modified as above may be further modified to have a columnar heat sink provided so as to coincide the axis thereof with an optical axis of the light receiving lens. The heat sink has fixed on one end plane thereof the light receiving element, and has fixed on the side plane thereof the light emitting element.

[0027] In such optical device for bar-code reading, the light receiving element fixed on one end plane of the heat sink opposes with the light receiving lens on the optical axis thereof. This means that the optical device can receive focused light from the light receiving lens in an efficient manner. On the other hand, the light emitting element fixed on the side plane of the heat sink can desirably prevent the light from the light emitting element from going into the entire portion of the light receiving lens, which allows irradiation of the light only in a portion of the receiving lens having incorporated therein the light projection lens. Accordingly, the light emitted from the light emitting element and reflected from a bar code after irradiation thereof can directly be received by the light receiving element attached on the heat sink without need of 90° bending of the optical path using a mirror or the like.

[0028] A method for manufacturing an optical device for bar-code reading according to the first aspect of the present invention is characterized by comprising the steps of fitting a light projection lens into a penetrating hole formed in a receiving lens so as to penetrate a plane of incidence of light and a plane of outgoing of light in a manner freely movable along the optical axis of the light projection lens; fixing the light receiving lens after positioning it relative to a light receiving element; and fixing the light projection lens after positioning it relative to the positioned and fixed light receiving lens.

[0029] In the manufacturing method, the light projection lens is positioned by moving it relative to the light receiving lens after positioning and fixing the light receiving lens relative to the light receiving element. Accordingly, moving of the light projection lens to be performed later will never dislocate the light receiving lens which is positioned in advance. In other words, the individual lenses can be positioned at optimum positions. This allows the individual lenses to be finely positioned, which has not been practical for the conventional integrated mold lens, and can improve accuracy in assembly of the optical device for bar-code reading and in reading while concomitantly attaining downsizing and weight reduction.

[0030] A light projection/receiving package according to a second aspect of the present invention is such that for irradiating light emitted from a light emitting element to a target object to be irradiated, and for receiving reflected light from the target object using a light receiving element, and is characterized in that the light emitting element and light receiving element are mounted on front and rear planes of a single die pad.

[0031] Since the light projection/receiving package is composed so that the light emitting element and the light receiving element are mounted back to back on the front and rear planes of the single die pad, it is no more necessary to keep both areas for mounting the light emitting element and the light receiving element on one plane (on the same plane) of the die pad. This means that it will be sufficient to use a die pad affording a mounting area for the light receiving element, which generally requires a larger mounting area, and this intrinsically allows mounting of the light emitting element on the opposite plane. Accordingly, the die pad in this case will be smaller than that having on one plane both of the light emitting element and the light receiving element. This successfully results in downsizing and weight reduction of the light projection/receiving package.

[0032] The light projection/receiving package according to a third aspect of the present invention is characterized by comprising a die pad; a light emitting element and a light receiving element respectively mounted back to back on the front and rear planes of the die pad; an optical path bending means provided on one plane of the die pad on which the light emitting element is mounted so as to bend an advancing direction of the emitted light from the light emitting element approximately at right angles; and a penetrating hole formed in the die pad so as to allow the light having the advancing direction bent by the optical path bending means to pass through towards the other plane of the die pad on which the light receiving element is mounted.

[0033] In the light projection/receiving package, when the light emitted from the light emitting element in a direction parallel to the plane of the die pad comes into the optical path bending means, the optical path thereof is bent approximately at right angles so as to have a direction perpendicular to the plane of the die pad. The directed light passes through the penetrating hole formed in the die pad, to thereby reach the plane opposite to that having the light emitting element mounted thereon, that is the plane having mounted thereon the receiving element. Accordingly, the optical path of the light from the light emitting element can be bent towards the opposite plane within a limited area on the die pad plane, without providing any optical means for bending the optical path outside the die pad.

[0034] The light projection/receiving package may be modified to further comprises an integrated light projection/receiving lens having integrated therein a source lens portion and a light receiving lens portion, which is provided in parallel to the die pad on the side facing to the plane thereof on which the light receiving element is mounted.

[0035] In the light projection/receiving package, the light emitted after passing through the penetrating hole is focused by the light projection lens portion and then irradiated to the target object to be irradiated. The reflected light returned back from the target object is focused by the light receiving lens portion and then goes into the light receiving element. In other words, only one integrated light projection/receiving lens portion is responsible for focusing of the emitted light and the reflected light, which is beneficial in that reducing the number of parts for the optical means and man-hour for the assembly. Since the emitted light and the reflected light are directed perpendicular to the die pad, the light projection/receiving package is also advantageous in that only a simple assembly of the integrated light projection/receiving lens on the die pad in parallel thereto can readily align the center axes of the light projection lens portion and the light receiving lens potion in parallel to the optical axes of the emitted light and the reflected light.

[0036] The light projection/receiving package may further be modified so the receiving element is provided in the number of two; the die pad has the penetrating hole between the two light receiving elements; and the integrated light projection/receiving lens has the receiving lens portion in the number of two, and the light projection lens portion formed between the two light receiving lenses.

[0037] The light projection/receiving package has two light receiving elements and two light receiving lens portions on one plane of the die pad, which successfully improves light receiving sensitivity. Since the penetrating hole is formed in the die pad between both light receiving elements, and the light projection lens portion is formed between the light receiving lens portions, the package is also advantageous in that surely providing the light emitting assembly only within a space for forming the light receiving assembly. Accordingly, such constitution in which the light emitting element and the light receiving element are mounted on the front and rear planes will more efficiently contribute to the space saving.

[0038] The light projection/receiving package pf the third aspect of the invention may be modified so that the package has a front wall in parallel to the die pad on the side facing to the plane thereof on which the light receiving element is mounted; and the light projection lens opposed to the penetrating hole and the light receiving lens opposed to the light receiving element are separately provided on the front wall.

[0039] The light projection/receiving package has the light projection lens and the light receiving lens in a separated manner, which is beneficial in that completely preventing generation of extraneous light (stray light) caused by diffraction or dispersion from the light projection lens portion towards the light receiving lens portion. The extraneous light is likely to generate for a case the integrated light projection/receiving lens made of a single kind of medium is used. The separate provision of the light projection lens and the light receiving lens allows material selection and coating optimized for the individual lenses, which raises the degree of freedom in lens design, and also allows independent positional adjustment thereof, which improves accuracy in the adjustment.

[0040] The light projection/receiving package may be modified to further comprises a partition wall formed between the die pad and the front wall of the package so as to isolate an emissive optical path space between the penetrating hole and the light projection lens from an incident optical path space between the light receiving lens and the light receiving element.

[0041] Since the emissive optical path space and the incident optical path space are isolated by the partition wall in the light projection/receiving package, the light emitted from the penetrating hole will never leak from the emissive optical path space to the incident optical path space. This arrangement completely prevents the light emitted from the light emitting element from becoming the extraneous light for the light receiving element. This improves the light receiving sensitivity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above and other objects, features and advantages of the present invention will become more apparent from the following description of the presently preferred exemplary embodiment of the invention taken in conjunction with the accompanying drawings, in which:

[0043]FIG. 1 is a sectional view showing a principal portion of an optical device for bar-code reading according to the present invention;

[0044]FIG. 2 is a front view of the optical device for bar-code reading shown in FIG. 1;

[0045]FIGS. 3A and 3B are a partly sectional view and a front view, respectively, of a light receiving lens as a single element shown in FIG. 1;

[0046]FIGS. 4A and 4B are a partly sectional view and a front view, respectively, of the assembled light receiving lens having inserted therein a light projection lens shown in FIG. 1;

[0047]FIGS. 5A and 5B are a partly sectional view and a front view, respectively, of a modified example of the light projection lens as a single element;

[0048]FIG. 6 is a sectional view for explaining an operational status of the optical device for bar-code reading shown in FIG. 1;

[0049]FIG. 7 is a sectional view of a first embodiment of a light projection/receiving package according to the present invention;

[0050]FIG. 8 is a drawing taken along the VIII-VIII line in FIG. 7;

[0051]FIG. 9 is a drawing taken along the IX-IX line in FIG. 7;

[0052]FIG. 10 is a drawing taken along the X-X line in FIG. 9;

[0053]FIG. 11 is a drawing for explaining operation of the light projection/receiving package shown in FIG. 7;

[0054]FIG. 12 is a sectional view showing a second embodiment of the light projection/receiving package according to the present invention;

[0055]FIG. 13 is a drawing for explaining operation of the optical device for bar-code reading shown in FIG. 12;

[0056]FIG. 14 is a sectional view showing a third embodiment of the light projection/receiving package according to the present invention;

[0057]FIG. 15 is a drawing taken along the XV-XV line in FIG. 14;

[0058]FIG. 16 is a drawing taken along the XVI-XVI line in FIG. 14;

[0059]FIG. 17 is a drawing taken along the XVII-XVII line in FIG. 16;

[0060]FIG. 18 is a drawing for explaining operation of the light projection/receiving package shown in FIG. 14;

[0061]FIG. 19 is a schematic drawing for explaining a conventional optical reading system; and

[0062]FIG. 20 is a sectional view of a conventional optical device for bar-code reading.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] Preferred embodiments of an optical device for bar-code reading and a method for manufacturing thereof according to the present invention will be detailed hereinafter referring to the attached drawings. FIG. 1 is a sectional view showing a principal portion of an optical device for bar-code reading according to the present invention, and FIG. 2 is a front view of the optical device for bar-code reading shown in FIG. 1.

[0064] An optical device for bar-code reading (referred to as “scan engine” hereinafter) 31 according to the present embodiment has an integrated constitution of a light emitting assembly and a light receiving assembly, which have conventionally been separated members. More specifically, on one surface of a disc-formed substrate 33, a heat sink 35 having a form of square rod is fixed so as to coincide the axis thereof with the center of the substrate. Electrical connection with the heat sink 35 is attained by a heat sink lead 37 a a penetrating the substrate 33.

[0065] On the end plane of the heat sink 35 opposite to the plane fixed to the substrate, a light receiving element 39 is fixed. The receiving element 39 operates so as to essentially receive light coming from the front in an axial direction of the heat sink 35, and subject the light to photo-electric conversion. The light receiving element 39 is electrically connected to a light receiving element lead 37 b penetrating the substrate 33 through a bonding wire 41.

[0066] On the other hand, on a side plane of the heat sink 35, a light emitting element 43 is fixed. Accordingly, the light emitting element 43 and light receiving element 39 are respectively provided on orthogonal planes 90° away from each other. Also the light emitting element 43 is electrically connected to a light emitting element lead 37 c penetrating the substrate 33.

[0067] On the plane of the substrate 33 on which the heat sink 35 is fixed, a cylindrical casing 45 having an outer diameter approximately same as that of the substrate 33 is fixed in a concentric manner. That is, the heat sink 35, the light receiving element 39 and the light emitting element 43 are housed in the casing 45. At an opened end (right end in the drawing) of the casing 45, a light receiving lens 47 having an outer diameter approximately same as that of the casing 45 is fixed concentrically with the heat sink 35. The light receiving lens 47 is responsible for focusing the reflected light from a bar code, not shown, towards the light receiving element 39.

[0068]FIGS. 3A and 3B are a partly sectional view and a front view, respectively, of the receiving lens as a single element shown in FIG. 1, FIGS. 4A and 4B are a partly sectional view and a front view, respectively, of the assembled receiving lens having inserted therein a light projection lens shown in FIG. 1, and FIGS. 5A and 5B are a partly sectional view and a front view, respectively, of a modified example of the light projection lens as a single element. The light receiving lens 47 has formed, in a portion opposing to the light emitting element 43, a penetrating hole 51 penetrating a plane of incidence of light 47 a and a plane of outgoing of light 47 b in parallel to the optical axis. In the penetrating hole 51, a light projection lens 53 is inserted.

[0069] The light projection lens 53 according to the present embodiment is composed as a compound lens which comprises a plurality of single lenses 55 a, 55 b. The single lenses 55 a, 55 b are housed in a cylinder 57 so as to make an optical axes thereof coincide with an axial line. The light projection lens 53 is incorporated into the light receiving lens 47 in an integrated manner by inserting the cylinder 57 into the penetrating hole 51. The light projection lens 53 is composed so that light can propagate in an almost parallel form between two single lenses 55 a, 55 b, which ensures a large allowance for the dislocation of the axis in a direction perpendicular to the optical axis, and is beneficial in improving the production yield or reliability.

[0070] Before completion of attachment of the light projection lens 53 into the light receiving lens 47, the cylinder 57 is fitted to the penetrating hole 51 so as to freely movable along the axial line. It is also allowable for the light projection lens 53 that the single lenses 55 a, 55 b are fitted so as to be freely movable in the cylinder 57. This allows the light projection lens 53 to be adjusted relative to the light receiving lens 47 within a movable range of the cylinder 57. After the light projection lens 53 is properly positioned at a predetermined position, the cylinder 57 or the single lenses 55 a, 55 b are fixed using an adhesive or the like.

[0071] Since the light projection lens 53 is composed so that a plurality of single lenses 55 a, 55 b are fitted within the cylinder 57, and the cylinder 57 is inserted in the penetrating hole 51 of the light receiving lens 47, a variety of positional adjustment of the lenses will be available, for example, such that moving the whole compound lens, previously fabricated so as to arrange the single lenses 55 a, 55 b within the cylinder 57 at regular intervals, relative to the penetrating hole 51, or such that moving arbitrary single lenses 55 a, 55 b relative to the cylinder 57 while keeping the cylinder 57 being fixed in the penetrating hole 51.

[0072] The cylinder 57 is preferably composed of a metal material. By composing the cylinder with a metal, light which comes from the light emitting element 43 and goes into the light projection lens 53 will never propagate from the inner circumferential surface of the penetrating hole 51 towards a medium of the light receiving lens 47. Accordingly, it is no more probable that the light from the light emitting element 43 comes into the receiving element 39 to cause extraneousness. This means that the light receiving element 39 can gain a higher receiving accuracy of the reflected light.

[0073] To fabricate thus composed scan engine 31, the light receiving lens 47 is first positioned relative to the light receiving element 39. Setting a height h of the heat sink 35 above the substrate 33 and a height H of the casing 45 at predetermined values can effected the positioning. The light projection lens 53 is then adjusted by moving it relative to thus positioned and fixed light receiving lens 47, and finally fixed to the penetrating hole 51 using an adhesive or the like when a predetermined position is found.

[0074] Besides that described in the above, the light projection lens 53 can be composed only of a cylindrical single lens 55 c as shown in FIGS. 5A and 5B. Such composition of the light projection lens 53 with the single lens 55 c will facilitate the manufacturing process as compared with that of the compound lens. The cylindrical shape thereof will be also beneficial in that facilitating the insertion of the light projection lens 53 per se into the penetrating hole 51, and thus enabling fixation of the light projection lens 53 to the light receiving lens 47 in a manner freely movable along the optical axis without using any other members (for example, the foregoing cylinder 57).

[0075]FIG. 6 is a sectional view for explaining an operational status of the scan engine shown in FIG. 1. In the scan engine 31 according to the present embodiment, once the light emitting element 43 is activated by an emission drive circuit not shown, the emitted light is focused by the light projection lens 53 and then emitted out from the emission end of such light projection lens 53. The emitted light irradiates a bar code not shown, and then, is reflected by the bar code, is directed to the light receiving lens 47 to be focused, and is received by the light receiving element 39. The light receiving element 39 subjects the received light to photo-electric conversion to thereby convert a bar code pattern into electric signals, and then outputs them through the light receiving element lead 37 b. A not shown computer then processes the output signals for decoding.

[0076] As has been described in the above, in the scan engine 31, or the optical device for bar-code reading according to the present invention, the space for mounting the light receiving lens 47 intrinsically contains the space for mounting the light projection lens 53, since the penetrating hole 51 is formed in the light receiving lens 47 and the light projection lens 53 is inserted into the penetrating hole 51. Accordingly, it is no more necessary to keep space for mounting for every lens, which results in downsizing and weight reduction. In addition, it allows selection of material and coating or so optimized for each lens to thereby raise the degree of freedom in the design. It is also advantageous since relative position of the light projection lens 53 and the light receiving lens 47 can be adjusted, positional errors of the individual lenses relative to the individual elements (light emitting element 53 and light receiving element 47) can surely be absorbed (minimized).

[0077] Preferred embodiments of a light projection/receiving package for bar-code reading according to a second aspect of the present invention will be detailed hereinafter referring to the attached drawings. FIG. 7 is a sectional view of a first embodiment of a light projection/receiving package according to the present invention; FIG. 8 is a drawing taken along the VIII-VIII line in FIG. 7; FIG. 9 is a drawing taken along the IX-IX line in FIG. 7; and FIG. 10 is a drawing taken along the X-X line in FIG. 9.

[0078] A light projection/receiving package 131 typically has a resin-made outer shell having a form of square-sectioned pipe opened at both ends. The light projection/receiving package 131 has inside thereof a die pad 133 which isolates an inner housing space of the light projection/receiving package 131 into a front housing chamber 135 and a rear housing chamber 137. The rear housing chamber 137 houses a light emitting element 139 mounted on a rear plane of the die pad 133. The light emitting element 139 has a monitoring PD (photodiode), not shown, for controlling the laser output to a predetermined level.

[0079] In the vicinity of the light emitting element 139, an optical path bending means (fixed 45° mirror) 141 for bending an advancing direction of light emitted from the light emitting element 139 approximately by 90° is mounted. Substituting the fixed 45° mirror 141 with a prism can also give a similar optical path. In the vicinity of the fixed 45° mirror 141, a penetrating hole 143 penetrating the die pad 133 is formed, which allows the light, having its advancing direction already bent by the fixed 45° mirror 141, to pass therethrough towards the opposite (front) plane of the die pad 133 (the right side in FIG. 7).

[0080] The light projection/receiving package 131 has two light receiving elements 145, 145 in order to improve receiving sensitivity. More specifically, the front housing chamber 135 houses two light receiving elements 145, 145 mounted on a front plane of the die pad 133. In other words, the light projection/receiving package 131 has housed therein the light emitting element 139 and the light receiving elements 145, 145 arranged back to back on the die pad 133. The foregoing penetrating hole 143 formed in the die pad 133 is located between the two light receiving elements 145, 145.

[0081] As shown in FIGS. 8 and 9, the light projection/receiving package 131 has a plurality of leads 149 penetrating both side planes of a wall portion 147 to thereby project out therefrom (4 leads each from the left and right planes, total 8 leads, in this embodiment). Four leads 149 a, 149 b, 149 c and 149 d projected out from one side plane expose only in the rear housing chamber 137, and are connected to the individual electrodes of the light emitting element 139. Another four leads 149 e, 149 f, 149 g and 149 h projected out from the opposite side plane expose only in the front housing chamber 135, and are connected to the individual electrodes of the light receiving elements 145, 145 through bonding wires. The electrodes of the light emitting element 139 and the light receiving element 145 are thus drawn out from the light projection/receiving package 131 via the leads 149.

[0082] The light projection/receiving package 131 can typically be mounted on a circuit board 151 as shown in FIG. 10, in which all leads 149 are bent backward at right angles, and connected and fixed to a circuit formed on the circuit board 151 using solder or the like.

[0083] Since the leads 149 a, 149 b, 149 c and 149 d connected to the light emitting element 139 are exposed only in the rear housing chamber 137 housing therein the light emitting element 139, and the leads 149 e, 149 f, 149 g and 149 h connected to the receiving elements 145, 145 are exposed only in the front housing chamber 135 which houses the receiving elements 145, 145, so that even a small housing space can successfully improve isolating property between the emitting element leads 149 a, 149 b, 149 c and 149 d and the light receiving element leads 149 e, 149 f, 149 g and 149 h.

[0084] The light projection/receiving package 131 supports an integrated light projection/receiving lens 153, which comprises a light projection lens portion 153 a and two receiving lens portions 153 b, 153 b integrated therewith, in parallel to the die pad 133 on the side facing to the plane thereof on which the light receiving elements 145, 145 are mounted. The integrated light projection/receiving lens 153 is composed by forming two light receiving lens portions 153 b, 153 b and forming one light projection lens portion 153 a between them.

[0085] The integrated light projection/receiving lens 153 can be formed using transparent resin such as polycarbonate, or glass. The integrated light projection/receiving lens 153 is designed so as to be positioned and fixed in parallel to the die pad 133 by placing it on the opened end of the front housing chamber 135 and by fixing with an adhesive. The integrated light projection/receiving lens 153 is responsible for focusing the light emitted through the penetrating hole 143 to thereby irradiate a bar code using the light projection lens portion 153 a, and is also responsible for focusing the reflected light returned from the bar code to thereby direct the light towards the light receiving elements 145, 145 using the light receiving lens portions 153 b, 153 b. In other words, only one integrated light projection/receiving lens 153 is responsible both for focusing of the emitted light and for focusing of the reflected light. The integrated light projection/receiving lens 153 is also advantageous in that facilitating the assembly thereof by simply placing it on the opened end of the casing to thereby align itself in parallel to the die pad 133, so as to align the center axes of the light projection lens portion 153 a and the light receiving lens potion 153 b in parallel to the optical axes of the emitted light and the reflected light.

[0086]FIG. 11 is a drawing for explaining operation of the light projection/receiving package shown in FIG. 7. In thus composed light projection/receiving package 131, the light emitted from the light emitting element 139 changes the advancing direction thereof by 90° with the aid of the fixed 45° mirror 141, passes through the penetrating hole 143, and then, is focused by the light projection lens portion 153 a of the integrated light projection/receiving lens 153 and is emitted. The emitted light is then reflected on a mirror of a scan mirror, not shown, and allowed to irradiate a bar code.

[0087] The light irradiated to the bar code returns back to the mirror with an intensity variation caused by a black-and-white pattern of the bar code while being affected by some irregular reflection, the light reflected there then goes into the light receiving lens portions 153 b, 153 b of the integrated light projection/receiving lens 153. The light went into the receiving lens portions 153 b, 153 b is focused and is then received by the light receiving elements 145, 145. The light receiving elements 145, 145 subject the light to photo-electric conversion to thereby converts a bar code pattern into electric signals, and then output them through the leads 149 e, 149 f, 149 g, 149 h. A not shown computer receives the output signals and processes them for decoding the bar code information.

[0088] Since the light projection/receiving package 131 is composed so that the light emitting element 139 and the light receiving elements 145, 145 are mounted back to back on the front and rear planes of the single die pad 133, it is no more necessary to keep both areas for mounting the light emitting element 139 and the light receiving elements 145, 145 on one plane (same plane) of the die pad 133. That is, it will be sufficient to use a die pad 133 affording a mounting area for the light receiving elements 145, 145, which generally require a larger mounting area, and this intrinsically allows mounting of the light emitting element 139 on the opposite plane. Accordingly, the die pad 133 in this case can be downsized by an area for mounting the light emitting element 139, which successfully results in downsizing and weight reduction of the light projection/receiving package 131.

[0089] Since the optical path of the light emitted from the light emitting element 139 is bent approximately at right angles by the fixed 45° mirror 141 and thus bent light is directed through the penetrating hole 143 towards the opposite side of the die pad 133, it is no more necessary to provide any optical means for bending the optical path outside the die pad 133, and the change in the optical path of the light from the light emitting element 139 towards the opposite side can be accomplished only in a limited area on the die pad plane.

[0090] The light projection/receiving package provided with the two light receiving elements 145, 145 and two light receiving lens portions 153 b, 153 b on one plane of the die pad 133, which successfully improves the receiving sensitivity. Since the penetrating hole 143 is formed in the die pad 133 between both light receiving elements 145, 145, and the light projection lens portion 153 a is formed between the receiving lens portions 153 b, 153 b, the package is also advantageous in that surely providing the light emitting assembly only within a space for forming the light receiving assembly. Accordingly, the constitution in which the light emitting element 139 and the light receiving elements 145, 145 are mounted on the front and rear planes will more efficiently contribute to the space saving. More specifically, the package of the present embodiment having two or more light receiving elements 145 for a single light emitting element 139 will exhibit a more distinctive space-saving effect as compared with that exhibited by the package having only one light receiving element 145 for a single light emitting element 139.

[0091] Next paragraphs will describe a second embodiment of the light projection/receiving package according to a second aspect of the present invention. FIG. 12 is a sectional view showing a second embodiment of the light projection/receiving package according to the present invention, and FIG. 13 is a drawing for explaining operation of the optical device for bar-code reading shown in FIG. 12. It should now be noted that members similar to those shown in FIGS. 7 to 12 will have the same reference numerals, and will not be detailed again.

[0092] In a light projection/receiving package 161 according to the present embodiment, a light emitting element 139 and a fixed 45° mirror 141 are mounted on a rear plane of a die pad 163, the die pad 163 has formed therein a penetrating hole 143, and a light receiving element 145 is mounted on a front plane of the die pad 163. Over the front plane of the die pad 163, an integrated light projection/receiving lens 165, which comprises one light projection lens portion 165 a and one light receiving lens portion 165 b, is opposed in parallel to the die pad 163. In other words, the light projection/receiving package 161 has an all-in-one structure containing the light receiving element 145 and the light receiving lens portion 165 b for focusing the reflected light on the light receiving element 145.

[0093] Also in the light projection/receiving package 161, shown in FIG. 13, light emitted from the light emitting element 139 changes an advancing direction thereof by 90° by a fixed 45° mirror 141, passes through the penetrating hole 143, and is focused by the light projection lens portion 165 a of the integrated light projection/receiving lens 165 and is then emitted. The emitted light is then reflected on a mirror of a scan mirror, not shown, and allowed to irradiate a bar code. The light irradiated on the bar code plane returns back to the mirror, goes into the light receiving lens portion 165 b of the integrated light projection/receiving lens 165 to be focused, and then received by the light receiving element 145.

[0094] Although the light projection/receiving package 161 will be slightly lower in the receiving sensitivity than the foregoing light projection/receiving package 131, the die pad 163 and the integrated light projection/receiving lens 164 can be made smaller, which promotes further downsizing and weight reduction.

[0095] A third embodiment of the light projection/receiving package according to a second aspect of the present invention will be described. FIG. 14 is a sectional view showing a third embodiment of the light projection/receiving package according to the present invention. FIG. 15 is a drawing taken along the XV-XV line in FIG. 14. FIG. 16 is a drawing taken along the XVI-XVI line in FIG. 14, and FIG. 17 is a drawing taken along the XVII-XVII line in FIG. 16. It should now be noted that members similar to those shown in FIGS. 7 to 11 will have same reference numerals, and will not be detailed again.

[0096] A light projection/receiving package 171 according to the present embodiment, shown in FIGS. 14 and 15, has a die pad 173, on a rear plane of which the light emitting element 139 and a fixed 45° mirror 141 are mounted, the die pad 173 itself has a penetrating hole 143 formed therein, and on the front plane of which one light receiving element 145 is mounted.

[0097] On the side facing to the plane of the die pad 173 on which the light receiving element 145 is mounted, a front package wall 175 is provided in parallel to the die pad 173. As shown in FIG. 16, the front package wall 175 has a light projection lens attachment hole 177 aligned concentrically with the penetrating hole 143, and a square light receiving window 179 for allowing the receiving element 145 to expose therethrough. The front package wall 175 has a light projection lens 181 and a light receiving lens 183, which are provided as separate members, as being attached to the light projection lens attachment hole 177 and the light receiving window 179, respectively.

[0098] The light projection lens attachment hole 177 has formed thereto a fitting portion for a convenience of attaching the light projection lens 181. The light projection lens 181 is slid along the axial direction of the fitting portion to complete a necessary focus adjustment, and the outer periphery thereof is then fixed by adhesion to the fitting portion. This ensures agreement of optical axes and focal points between the light emitting element 139 and light projection lens 181 in a simple and accurate manner. Also the light receiving window 179 has formed thereto a fitting portion for a convenience of attaching the light receiving lens 183. By fitting the light receiving lens 183 to the fitting portion, the optical axis and focus of the light receiving lens 183 will readily be agreed with those of the light receiving element 145.

[0099] As shown in FIGS. 15 and 16, the light projection/receiving package 171 has six leads 185 in total, in which each three leads penetrates the wall portion 147 on both sides. Three leads 185 a, 185 b and 185 c projected out from one side plane expose only in a rear housing chamber 137, and are connected through bonding wires 187 to the individual electrodes of the light emitting element 139. Another three leads 185 d, 185 e and 185 f projected out from the opposite side plane expose only in a front housing chamber 135, and are connected to the individual electrodes of the light receiving element 145 through the bonding wires 189.

[0100] The light projection/receiving package 171 can typically be mounted on a circuit board 151 as shown in FIG. 17, in which all leads 153 are bent backward at right angles, and connected and fixed to a circuit formed on the circuit board 151 using solder or the like.

[0101] The light projection/receiving package 171 has a partition wall 195 formed between the die pad 173 and the front package wall 175 so as to isolate an emissive optical path space 191 between the penetrating hole 143 and light projection lens 181 from an incident optical path space 193 between the light receiving lens 183 and the light receiving element 145. Accordingly, the light emitted from the light emitting element 139 and reached the emissive optical path space 191 after passing through the penetrating hole 143 will never leak into the incident optical path space 193.

[0102]FIG. 18 is a drawing for explaining operation of the light projection/receiving package shown in FIG. 14. In thus composed light projection/receiving package 171, the light emitted from the light emitting element 139 changes an advancing direction thereof by 90° with the aid of the fixed 45° mirror 141, passes through the penetrating hole 143, is focused by the light projection lens 183 and is then emitted. The emitted light is then reflected on a mirror 197 of a scan mirror 196, and allowed to irradiate a bar code not shown.

[0103] The light irradiated to the bar code returns back to the mirror 197 with an intensity variation caused by a black-and-white pattern of the bar code while being affected by some irregular reflection, the light reflected there then goes into the light receiving lens 183. The reflected light went into the light receiving lens 183 is focused and is then received by the light receiving element 145. The light receiving element 145 subjects the light to photo-electric conversion to thereby converts a bar code pattern into electric signals, and then outputs them through the leads 185 d, 185 e and 185 f.

[0104] The light projection/receiving package 171 has not only a basic effect of attaining downsizing and weight reduction similarly to the light projection/receiving packages 131, 151 according to the foregoing first and second embodiments, but also has an effect of completely preventing generation of extraneous light (stray light) caused by diffraction or dispersion from the light projection lens portion towards the receiving lens portion, which extraneous light is likely to generate for a case the integrated light projection/receiving lens made of a single kind of medium is used, since the light projection lens 181 and the light receiving lens 183 are separately provided. Such separate provision of the light projection lens 181 and the light receiving lens 183 also allows material selection and coating optimized by the individual lenses, which raises the degree of freedom in the lens design, and still also allows independent positional adjustment thereof, which improves accuracy in the adjustment.

[0105] Since the emissive optical path space 191 and the incident optical path space 193 are isolated by the partition wall 195, the light emitted from the penetrating hole 143 will never leak from the emissive optical path space 191 to the incident optical path space 193, which completely prevents the light emitted from the light emitting element 139 from becoming the extraneous light for the light receiving element 145. This improves the receiving sensitivity. 

What is claimed is:
 1. An optical device for bar-code reading comprising: a light emitting element; a light projection lens for focusing light from said light emitting element so as to irradiate a bar code; a light receiving lens for focusing reflected light from the bar code and having formed therein a penetrating hole which penetrates a plane of incidence of light and a plane of outgoing of light, in which said light projection lens is inserted; and a light receiving element for receiving the light focused by said light receiving lens so as to perform photo-electric conversion.
 2. The optical device for bar-code reading as claimed in claim 1, wherein said light projection lens is a compound lens in which a plurality of single lenses are combined.
 3. The optical device for bar-code reading as claimed in claim 2, wherein said plurality of single lenses are fitted within a cylinder so that an optical axis of said lenses coincides with an axis of said cylinder, and said cylinder is inserted in said penetrating hole of said light receiving lens.
 4. The optical device for bar-code reading as claimed in claim 3, wherein said cylinder is made of a metal.
 5. The optical device for bar-code reading as claimed in claim 1, wherein said light projection lens is a cylindrical single lens.
 6. The optical device for bar-code reading as claimed in any one of claims 1 to 5, further comprising a columnar heat sink provided so as to coincide an axis thereof with an optical axis of said light receiving lens, wherein said heat sink has fixed on one end plane thereof said light receiving element, and has fixed on a side plane thereof said light emitting element.
 7. A method for manufacturing an optical device for bar-code reading, comprising the steps of: fitting a light projection lens into a penetrating hole formed in a light receiving lens so as to penetrate a plane of incidence of light and a plane of outgoing of light in a manner freely movable along an optical axis of said light projection lens; fixing said light receiving lens after positioning said light receiving relative to a light receiving element; and fixing the light projection lens after positioning the light projection lens relative to said positioned and fixed light receiving lens.
 8. A light projection/receiving package for irradiating light emitted from a light emitting element to a target object to be irradiated, and for receiving reflected light from said target object using a light receiving element, wherein said light emitting element and said light receiving element are mounted on front and rear planes of a single die pad.
 9. A light projection/receiving package comprising: a die pad; a light emitting element and a light receiving element respectively mounted back to back on front and rear planes of said die pad; an optical path bending means provided on one plane of said die pad on which said light emitting element is mounted so as to bend an advancing direction of the emitted light from said light emitting element approximately at right angles; and a penetrating hole formed in said die pad so as to allow the light having the advancing direction bent by said optical path bending means to pass through towards the other plane of said die pad on which said receiving element is mounted.
 10. The light projection/receiving package as claimed in claim 9, further comprising an integrated light projection/receiving lens having integrated therein a light projection lens portion and a light receiving lens portion, which is provided in parallel to said die pad on the side facing to the plane thereof on which said light receiving element is mounted.
 11. The light projection/receiving package as claimed in claim 10, wherein said light receiving element is provided in the number of two; said die pad has said penetrating hole between said two receiving elements; and said integrated light projection/receiving lens has said light receiving lens portion in the number of two, and said light projection lens portion formed between said two receiving lenses.
 12. The light projection/receiving package as claimed in claim 9, wherein said package has a front wall in parallel to said die pad on the side facing to the plane thereof on which said light receiving element is mounted; and said light projection lens opposed to said penetrating hole and said light receiving lens opposed to said light receiving element are separately provided on said front wall.
 13. The light projection/receiving package as claimed in claim 12, further comprising a partition wall formed between said die pad and said front wall of said package so as to isolate an emissive optical path space between said penetrating hole and said light projection lens from an incident optical path space between said light receiving lens and said light receiving element. 